As the technological development of semiconductors advances, demands for miniaturized packaging and larger data storage capacity have also intensified along the way. In addition to that, because the data processing capacity is constantly increasing, if data units of the same size can be processed at the fastest speed possible in a given unit of time, then data can be processed more efficiently. The most straightforward method for raising the processing speed of semiconductors is to increase its usage frequency, but when clock rates more then Gb/s, problems like power dissipation, signal time delay, and electromagnetic interference (EMI) also arise, which will impede the production of semiconductors with high performance. This problem has been made even more severe because the traditional medium for data signal transfer is copper circuit, which cannot achieve higher conductivity due to its intrinsically limited conducting property, thus its signal transmission speed cannot be elevated by the method of increasing its conductivity.
Moreover, the signal transmission structure made of metal circuits is more susceptible to the interference of external noises or internal circuits during signal transmitting, which in turn leads to erroneous signals being transferred. Therefore, the signal transmitting structure has to be equipped with adequate protective measures to prevent the interference mentioned above from affecting signals, and this phenomenon is especially obvious in high-frequency application. The protective measures will result in increased difficulty to the designs of circuit and additional structures, which will in turn raise the costs of design and production, and cannot improve the current situation.
The traditional method of signal transmitting is analog signal transmission, which works by charging conductor with electrical currents, but the current method for processing signals inside circuits is the digital processing method, which can easily distort signals when one type of signal is converted to the other during signal transfer.
In order to resolve the disadvantages resulted from the traditional method of analog signal transmission, the new technology uses optical signal to replace electrical signal for signal transmission, and the most palpable advantage by such change is better quality in signal transmission, since the optical signal is almost unsusceptible to interference of electromagnetic waves and is thus not distorted as much. As a result, there is no need to design a structure for preventing the interference of electromagnetic waves, and this helps reduce the costs of design and production. Therefore, using optical signal for signal transmission has become the main aim for future development.
In the prior arts, the optical signal transmission requires signal processing components such as optical fibers, optical connectors, optical/electrical converters, and electrical/optical converters for digital data transfer to proceed, but optical alignment system of high precision is large in size and hence can hamper the developmental trend of miniaturization.
FIG. 1 is a cross-sectional view showing the circuit board of U.S. Pat. No. 6,839,476, which utilizes optical fibers for signal transmission; wherein a core layer 12 is formed on the bottom layer 11, and a plurality of grooves 12a are formed on the core layer 12; an optical fiber 13 is placed into the groove 12a, then a top layer 14 is formed on core layer 12, so that optical fiber 13 is embedded inside core layer 12, and optical fiber 13 is made by enclosing a layer of cladding 13b around a core 13a. Optical transmitting and receiving modules or passive optical components can be disposed on both ends of optical fiber 13, by which allows optical fiber 13 to transfer optical signals, and thus avoiding the disadvantages resulted from electrical signal transfer.
However, because optical fiber 13 needs to be embedded in groove 12a of core layer 12, the core layer 12 has to undergo the grooving process in prior to the above step, followed by the disposition of optical fiber 13 into groove 12a to complete the overall production process. But the disposition of optical fiber 13 into groove 12a is carried out mechanically, in other words, the method of mechanical insertion is employed to insert electronic components into circuit board in prior arts. As a result, the speed of production is slower and cannot reach the goal of fast production.
Moreover, optical fiber 13 needs to be cut in accordance with the length of groove 12a that it faces beforehand, so that it can then be fit into groove 12a; this adds an additional step in the overall production process, and hence raises the difficulty of the production process. On the other hand, the uneven length of optical fiber 13 also makes the classification step in the production process more complicated, thereby increasing overall production steps and raising its complication, and in turn results in increased production costs.
Because grooves 12a has to be formed on core layer 12 in order to accept optical fiber 13, it is necessary to leave adequate interval spaces between each of the groove 12a while designing their size, so that optical fiber 13 can be fixed inside core layer 12. But under the double influences of the size of interval space and the diameter of optical fiber 13, the wiring density cannot be increased further.
Furthermore, the optical fiber 13 used to transfer optical signal is made by enclosing a layer of cladding 13b around a core 13a, wherein the inner layer of cladding 13b can serve as a reflective surface that allows the optical signals to be reflected forwardly and thereby achieving the goal of transmitting signals. However, optical fiber 13 and circuit board are two different structures and need to be made independently; afterwards, the two separately made products also have to be integrated. Both steps described above increase the difficulty of the overall production process as well as impede the attainment of mass production, and thus the production costs cannot be lowered further.
When precise alignment is carried out by the use of optical connector with optical fiber, the high precision aligning equipment is also required for the transfer of optical signal to proceed due to the lower performance of automatic production. In addition, it is also necessary to carry out aligning by manual labor, which leads to increased production costs and reduced productivity.
In addition, the semiconductor package of the prior arts is made by forming grooves inside it before implanting optical fibers, so it is necessary to leave adequate interval spaces between each of the groove while designing their size, so that optical fibers can be fixed inside the semiconductor package. But under the double influences of the size of interval space and the diameter of optical fiber, the wiring density cannot be further elevated, which also leads to more complicated and difficult production process, along with increased production costs.
Therefore, the most urgent issue for the industry is to provide an electronic device that can meet the demand of miniaturization and reduce loss of signal during signal transmitting, shorten conductivity pathway, and decrease noises; a circuit board integrated with optoelectronic components that can elevate signal transfer quality, increase registration, simplify production process, lower production costs, raise wiring density and productivity should also be provided.